Learning Forum

[Peter Yip]

Hello,

I am simulating an aluminum particle impacting an aluminum target, but getting the projectile traveling through the target as shown in my image. I read on LS-DYNA support that you can change the penalty scaling factor to adjust for this, however, even with large adjustments, I am still getting odd behavior. I feel like I am altering the solution too much by changing the penalty scaling factor so any additional notes on how this works is appreciated. Are there any other ideas on how to address this to make sure the projectile doesn't go through the material? 

Thanks,

Peter

[Armin]

 

Hi Peter,

Do you see this behavior only for the part of the projectile that is displayed with red circle in your picture? If so, it appears that a portion of the projectile which is eroded from the main part is passing through the target. You can check the *CONTROL_CONTACT card where the entry “enmass” indicates how eroded nodes should be treated. If this variable is set to zero, the eroded nodes are simply not considered in the contact algorithm that might be the problem in your case.

 

[Peter Yip]

Hi Armin,

That is correct. I only observe this behavior with what I have circled in the image. If I set the "enmass" entry to 1 (" eroding nodes of solid elements are retained and continue to be active in contact.") is that more realistic here?

I am a bit confused as to how the erosion criteria really works? For instance, when an element has been determined to erode it seems to be fully removed from the calculation, but is the mass redistributed to other nodes to conserve mass? Also, when a element erodes, the next neighbor exposed element will meet the surface and cause another stress wave to propagate which is not physical (to my understanding). Any insight here is appreciated.

Peter

[Armin]

Hi Peter,
In terms of how LS-DYNA considers energy balance after element erosion, I will refer you to the link below where more information is available.
https://www.dynasupport.com/howtos/general/total-energy

However, for your specific case, it appears to me that due to localized deformation (via shear banding, for example), a layer of elements in the projectile satisfies the condition for element erosion while the surrounding material is still below the threshold for erosion. As a result, a part of the projectile (shown with red circle) is detached and travels through the target. I think by setting enmass to 1, this issue could be resolved and it hopefully be better in line with what happens in reality.

[Loic Ivaldi]

Hello,

Can you screen your contact card ?

Try to lower the tssfac to see if the behavior is better.

Best Regards,
Loïc